"Don't call her that," Harry said sharply, but he shot Ron a look to try to quell him a little. Yelling at him probably wouldn't do much good. Though the way Kreacher was wailing, he might not even notice anyway.
Harry really didn't find it that hard to picture Mundungus making off with shite. He didn't exactly like the idea, but everything here was just lying about with no one using it. And it wasn't like Sirius had cared about any of it. Dung hadn't exactly seemed that upstanding a bloke, so selling off a bunch of old, useless pureblood stuff had probably seemed harmless enough. No one had paid much attention to Kreacher, really. Mundungus wouldn't be the exception to that.
"Who else is he going to tell? Technically the house is mine now, and the Order doesn't come through since Snape can get in." He probably didn't have anyone else to talk to. He was weird, and cranky and had betrayed them, and lied. But he was a miserable little thing. "Look, tell us what you know, all right? And we'll see what else we can get back for you. But tell us what you know - about the locket, and about Master Regulus." It tasted a little sour in his mouth, but after a moment he added. "Please."